1. Field of the Invention
The present invention relates to a method for producing a propylene-ethylene block copolymer.
2. Related Background Art
Because polypropylene resins used for automotive components, home electronic products, and the like are required to have high rigidity and high impact resistance, propylene block copolymers having a crystalline propylene polymer portion and an amorphous propylene polymer portion are typically used therefor. The propylene block copolymers are mainly produced by a method including a first polymerization process in which propylene is homopolymerized and a subsequent second polymerization process in which propylene and ethylene are copolymerized. More specifically, a method by which both the first polymerization process and the second polymerization process are performed by batch polymerization (see, for example, Japanese Patent Application Laid-open No. 6-136018), a method by which the first polymerization process is performed by continuous polymerization and the second polymerization process is performed by batch polymerization (see, for example, Japanese Patent Application Laid-open No. 61-101511), and a method by which both the first polymerization process and the second polymerization process are performed by continuous polymerization (see, for example, Japanese Patent Application Laid-open No. 10-168142) are known.